Wave motion in an isotropic elastic layer generated by a time-harmonic point load of arbitrary direction

Achenbach, Jan Drewes; Xu, Yi

doi:10.1121/1.427037

Cited by 93 publications

(41 citation statements)

References 11 publications

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“…However, the low attenuation properties of the S 0 and SH 0 modes mean that they cannot be efficiently excited or detected by transducers sensitive to out-of-plane surface motion. A point transducer that is sensitive to in-plane motion will excite and detect both the S 0 and SH 0 modes [22] but will not do so in an omnidirectional manner since, in transmission, the excitation force must be in a particular direction. The resulting field from such an element is shown schematically in Fig.…”

Section: Selection Of Transducer Elementmentioning

confidence: 99%

Omnidirectional guided wave inspection of large metallic plate structures using an EMAT array

Wilcox

Lowe

Cawley

2005

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

132

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The design of an electromagnetic acoustic transducer (EMAT) array device for the inspection of large areas of metallic plate-like structures using the S0 guided wave mode is described. The reasons for using the S0 mode are discussed and it is shown how the choice of mode determines the nature of the EMAT array elements. A novel array construction technique is shown to be necessary whereby the EMAT coils for adjacent elements are overlapped in order to achieve the required element density. Results are presented that illustrate the operation of the device on steel and aluminum plate specimens in the thickness range from 5 to 10 mm. An area of at least 10 m 2 can be inspected from a single location. Spurious signals in the results are caused both by the unwanted A0 mode and by S0 sidelobes, the latter occurring at the same radial distance from the array as the genuine S0 signal from a reflector, but in the wrong direction. The signal-to-coherent noise performance of the complete system is determined by the amplitude ratio of the largest genuine S0 signal to the largest spurious signal. This is typically around 30 dB. The sensitivity of the device to artificial defects and genuine corrosion patches is demonstrated and the limitations of its operation are discussed. The feasibility of using the device with the S1 guided wave mode to inspect a 20 mm thick plate is also demonstrated.

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Section: Selection Of Transducer Elementmentioning

confidence: 99%

Omnidirectional guided wave inspection of large metallic plate structures using an EMAT array

Wilcox

Lowe

Cawley

2005

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

132

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“…Assume that the incident wave is a plane wave of an n-th SH guided mode propagating with the direction (− ෝ), and the backscattered SH guided wave with the same mode as the incident wave is observed at the point = || ෝ. Then the incident wave and the Green's function ‫ܩ‬ are written as [4] () = i ‫ܣ‬ cos( ݊πܺ ଷ 2ܾ ) ݁ ି୧ ෝ⋅ ഥ (5)…”

Section: Inverse Scattering Of Guided Waves For Shape Reconstruction mentioning

confidence: 99%

Applications of approximate wave analysis to ultrasonic flaw imaging

Hirose

2013

2013 Far East Forum on Nondestructive Evaluation/Testing: New Technology and Application

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Two applications of approximate wave analyses to ultrasonic flaw imaging are presented. One is to apply a high frequency approximation for transmitted waves through curved interfaces to improve SAFT images of flaws in a structure with complex geometry. As examples, the improved SAFT is applied to pitchcatch data for flaws in an immersed round bar, and flaw images are compared with conventional SAFT images. Another application is to use a low frequency approximation to reconstruct a flaw shape of 3-D plate thinning from reflection coefficients of ultrasonic guided waves. By introducing a far field expression of Green's functions and Born approximation into the integral expression, a Fourier transform pair is obtained between the shape function of thinning flaw and reflection coefficients of backscattered guided waves. Some numerical examples are illustrated to show the validity and effectiveness of our inverse approach.

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“…On the basis of the derivation for wave motion generated by a time-harmonic point load [Achenbach 1999], [Ditri 1994b], Wilcox was able to link the point excitations of circular-crested waves to the line excitations of straight-crested waves [Wilcox 2004], [Wilcox 2005]. From Eqs.…”

Section: Excitation Of Circular-crested Guided Waves By Point Sourcesmentioning

confidence: 99%

Health Monitoring of Composite Structures Using Guided Waves

Rose¹

2012

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The public reportmg burd en for th1s collection of mform ation is estimated to average 1 hour per response. includmg the tim e for rev>ewing instruct>ons. searclhing exi sting data so urces. gathering and mmnta1mng the data needed . and co mpleting and rev1ew 1 ng the collection of 1nforma t1 on. Send co mments regarding th1s burden est1m ate or any other aspect o fth1s collection of mformat1on . 1nclud1 ng suggesti ons for reduc1 ng the burden. to the Department of De fense. ExecutiV e Serv1ce D>rectorate (0704 -0 188) Respo ndents should be aware that notwithstanding any other prov1 s1 on of law. no person shall be sub;ect to any penalty for falling to comply w1th a collect> on of 1 nform at1on if 1 t does not display a currently v alid OMB co ntrol number PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION. 1. REPORT DATE (DD-MM-YYYY)12. REPORT TYPE 3. DATES COVERED (From-To) PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATIONThe Pennsylvania State University REPORT NUMBER212 Earth-Engineering Sciences Building University Park, PA 16802 SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)Air Force Office of Scientific Research Aerospace, Chemical, and Material Sciences 875 N. Randolph Street Suite 325, Room 3112 SPONSOR/MONITOR'S REPORTArlington VA, 22203-1 768 NUMBER(S)AFRL-OSR-VA-TR-20 12-0264 DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited SUPPLEMENTARY NOTES ABSTRACTTwo guided wave SHM approaches were developed in this project. The first approach is based on a guided w ave tomographic technique, in which the region surrounded by a sparse sensor array is monitored. The second one is a phased array approach, in which sensors are attached to a structure in a compact format to form an array. The region subjected to inspection and monitoring is the region outside the array. Both techniques have shown an excellent capability of determining damage size, location, and severity. The importance of guided wave mode and frequency control has been demonstrated for both the tomography and the phased array approach. Guided wave annular arrays have been successfully developed as a means of mode and frequency control. Phased annular array transducers with excellent flexibility on guided wave mode tuning have also been investigated. Guided w ave tomography with improved robustness to environmental conditions w as demonstrated via the application of specially designed annular arrays. Damage detection using phased array beamforming was also achieved. Unique beamformer transducers were developed and applied to both isotropic and anisotropic multilayer composite structures.

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Wave motion in an isotropic elastic layer generated by a time-harmonic point load of arbitrary direction

Cited by 93 publications

References 11 publications

Omnidirectional guided wave inspection of large metallic plate structures using an EMAT array

Omnidirectional guided wave inspection of large metallic plate structures using an EMAT array

Applications of approximate wave analysis to ultrasonic flaw imaging

Health Monitoring of Composite Structures Using Guided Waves

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